Hydraulic control system

ABSTRACT

A HYDRAULIC SYSTEM HAVING CALIBRATION, BANDWIDTH, AND DAHS POT CONTROLS WITH INDICATORS FOR EACH, AND A DASH POT ADJUSTMENT.

1971 w. F. KELLER ETAL 3,620,185

HYDRAULIC CONTROL SYSTEM 3 Sheets-Sheet 3 Filed Sept. 8, 1969 III K r mm L urk 0 INVENTORJ. WILL/AM F. KELLER. FRANK F DOM VAN H T TOR NE" VNOV. 16, 1971 w, KELLER ETAL 3,620,185

HYDRAULIC CONTROL SYSTEM Filed Sept. 8, 1969 3 Sheets-Sheet 5 5 8 x V Y4/ I! l I l INVENTORS. l/V/LL/fl/M F KELLER BY FRANK F. DOM VAN UnitedStates U.S. Cl. 116-125 7 Claims ABSTRACT OF THE DISCLOSURE A hydraulicsystem having calibration, bandwidth, and dash pot controls withindicators for each, and a dash pot adjustment.

BACKGROUND OF THE INVENTION This invention relates to hydraulic systemsand, more particularly, to valve positioners or the like.

In the past, it has been the practice to calibrate a valve positioner byadjusting the position of a threaded shaft to vary the tension of afeedback spring. Such a device is disclosed in US Pat. No. 3,101,031.Such devices are inaccurate and have no visual indication ofcalibration.

Bandwidth adjustments are also old in the art; however, these haverequired clumsy adjustment procedures. Further, no bandwidth indicatorshave been provided with a correction which is a function of strokelength.

It is also old in the art to provide negative feedback to a valvepositioner and to adjust the feedback rate. However, such devices arecomplicated and have no visual indication of feedback rate.

SUMMARY OF THE INVENTION In accordance with the devices of the presentinvention, the above-described and other disadvantages of the prior artare overcome by providing a movable suspension system for the feedbackspring. The set point may, thus, be adjusted .accurately.

In accordance with a feature of the invention, a visual indication ofthe set point adjustment is provided.

According to another feature of the invention, a bandwidth adjustment isprovided including a lead screw and a nut therefore to operate afeedback lever.

Still another feature of the invention includes a bandwidth indicatorscale having a lined connecting plate extending from the nut to thescale. The plate may, thus, be adjusted to make the scale readaccurately for a particular length of stroke.

A further feature of the invention resides in the use of, for example, apneumatic bellows or feedback. The output of the bellows operates adiaphragm. The diaphragm chamber is vented through a needle valve whichcarries a scale to indicate the reset adjustments.

The above-described and other advantages of the invention will be betterunderstood from the following description when considered in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to beregarded as merely illustrative FIG. 1 is a vertical sectional view of ahydraulic control system constructed in accordance with the presentinvention;

FIG. 2 is a top plan view of a needle valve assembly shown in FIG. 1.

FIG. 3 is a perspective view, partially exploded, of a portion of theset point indicator of the present invention;

FIG. 4 is a side elevational view of a portion of the bandwidthadjustment and indicator of the present invention;

atent O ice FIG. 5 is a top plan view of the structure shown in FIG. 4;

FIG. 6 is a sectional view taken on the line 6-6 of a set screwadjustment shown in FIG. 5;

FIG. '7 is an enlarged broken away front elevational view of thebandwidth adjustment and index marker therefor;

FIG. 8 is a top plan view of the structure shown in FIG. 7; and

FIG. 9 is a vertical sectional view taken on the line 9-9 of thestructure shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a valve positioner isindicated at 10. The valve to be positioned is indicated at 11 in ahousing 12. Housing 12 includes a valve seat 13. Valve 11 is fixed to apiston rod 14. A piston 15 is fixed to rod 14. Cylinder 16 surroundspistons 15. Piston 15 has a groove 17 in which an O-ring 18 ispositioned. O-ring 18 seals the space between piston 15 and cylinder 16.Piston 15 is moved upwardly b'y fluid pressure supplied by a pump 19which is operated by an electric motor 20. The pressure below piston 15is determined by a hydraulic amplifier 21 which receives an input frompump 19 through a conduit 22. The lower end of cylinder 16 is suppliedwith [fluid under pressure by pump 19 through a conduit 23. Amplifier 21has outlet conduit 24 with an orifice 25. Hydraulic fluid is bled fromorifice 25 at a rate determined by the position of vane 26. Vane 26 isfixed to a beam 27. When amplifier 21 causes the pressure in conduit 23to drop by bleeding suflicient hydraulic fluid through orifice 25, aspring 28 closes valve 11.

A body 29 encloses rod 14 and a follower 30 for spring 28., follower 30being fixed to rod 14. Housing 29 is joined to an intermediate bodyportion 31 of positioner 10 at 32 and 33.

Positioner 10 has a body portion or end cover 34 and a body portion orside cover 35.

A divider and beam support 36 extends across body 31 near the upper endthereof. All of the structures shown in FIG. 1 below divider 36 may beentirely conventional. These devices may also operate in a conventionalway, for example, as shown and described in US. Pat. No. 3,087,471. Thusvalve 11 in this application corresponds to valve 10 in FIG. 5 in thepatent. Conduit 23 in this application corresponds to conduit 17 in thepatent. Piston 15 is the same in both. In the patent, a pump isindicated at 25, and a hydraulic amplifier is indicated between conduits20 and 63.

In this application, in end cap 34, a control mechanism 37 is shownincluding an arm 3 pivoted on a shaft 39 by a ball bearing 40 carriedthereby to rest on the upper end of piston rod 14. Ann 38 has a leadingscrew 41 threaded therethrough. Lead screw 41 may be turned to move anut '42. Nut 42 has a projection 43 on which another arm 44 rests. Arm44 is rotatable about a fixed shaft '45. An index marker 46 is alsofixed to nut 42. A spring '47 is fixed to the left end of beam 27. Theupper end of spring 47 is supported by a flexible strand 48. Strand 48'is movable over a pulley 49 with a nut 50. Nut 50 is moved by turning alead screw 51 carried by arm 44. Lead screw 51 is threaded through anindex marker 52.

Beam 27 is supported by flexure strips 53 and 54. A coil 55 is fixedtothe right end of beam 27. The entire construction of the positioner 10is made of nonmagnetic materials with the exception of a body 56. Body56 is made of a magnetic material.

A bellows 57 is located between arm 44 and a fixed projection 58.Bellows 57 has an output conduit 59 which extends into a chamber 60.Chamber 60 is enclosed with a diaphragm 61. Diaphragm 61 is connected tobeam 27 by a fixed member 62. Chamber 60 has an outlet conduit 63 inwhich a needle valve 64 is disposed.

In the operation of positioner shown in FIG. 1, the input is suppliedelectrically on leads 65 and 66 connected to coil 55. Piston will thenassume a position in accordance with the signal applied to leads 65 and66. Should there be any variation in the system so that piston 15assumes a position error, this will be reflected in a change in theposition of beam 27. This is true because the position of piston 15 and,therefore, piston rod 14 will cause arm 38 to move up or down byengagement of ball 40 with the upper end of rod 14. This, in turn, willcause arm 44 to move because arm 44 rests on projection 43 of nut 42.Movement of arm 44 will then cause the spring 47 to supply more or lessforce to the left end of beam 27. The force supplied by spring 47 is,thus, balanced against the force supplied by coil in its attraction forbody 56. Note will be taken that when beam 27 tilts in acounterclockwise direction, orifice 25 is closed by vane 26; and thepressure in conduit 23 is increased. Tilting of beam 27 in a clockwisedirection produces the opposite eflect.

In accordance with the present invention, downward movement of arm 44from the position shown causes bellows 57 to collapse. Downward movementof arm 44 is, therefore, retarded because air is not allowed to escapefrom bellows 57 except at a lower rate controlled by needle valve 64.Still further, negative feedback is provided in that the increasedpressure in chamber 60 causes a counterclockwise movement on beam 27through member 62.

It is a feature of the invention that bellows 57 is provided withchamber 60 for the negative feedback to provide damping. It is also afeature of the invention that needle valve 64 is provided to provide forthe damping, yet insures final accurate correction.

Another feature of the invention resides in the use of indicia 64' andan index marker 64" relative to needle valve 64 to indicate the resetaction adjustment of needle valve 64.

An adjustment card 67 is fixed to arm 38 by a screw 68. Card 67 has aslot 65! therethrough. Screw 68 extends through slot 69. The position ofcard 67 may be adjusted along the length of arm 38 by loosening screw 68and moving card 67 beneath screw 68. An index marker is provided on card67 at 70. Arm 38 has an indicia 71 thereon positioned so that indexmarker may be located relative thereto in a position corresponding tothe stroke of valve 11 desired for a particular input signal on leads 65and 66. In this position, by comparing marker 46 with indicia at 72 and73, the percentage of proportional bandwidth may be read from indicia 73on card 74 fixed to arm 38. The proportional bandwidth relates the rangeof input signal on leads 65 and 66 to the range thereon at a particularstroke setting.

Arm 44 has card 75 fixed thereto with indicia 76. Com parison of marker52 with indicia 76 gives the set point of the positioner 10.

An airtight O-ring seal 34' keeps valve 64 and all the structures in endcap 34 dirt free.

From the foregoing, it will be appreciated that, by the use of leadscrew 51, it is possible to adjust the set point accurately. Further,indicia 76 provide a visual indication of the set point adjustment. Abandwidth adjustment is also provided including lead screw 41.Percentage of bandwidth is indicated by indicia 73 for any given strokesetting of card 67. The arrangement of bellows 57 with diaphragm 61provides for negative feedback. Damping is simultaneously provided bybleeding air from bellows 17 through needle valve 74. The reset actionis visible through indicia 64'.

In FIG. 3, an ear 76 is fixed to arm 44 as is card 75 and a shaft 77.Shaft 77 has a flange 78 fixed thereto which holds pulley 49 on shaft77.

Nut 50 has an area 79 to which strand 48 is fixed, strand 48 and leadscrew 51 being omitted in FIG. 3 for clarity. Index marker 52 is fixedto a nut 80 which is exposed out of position for clarity. As shown, nuts50 and 80 have vertical surfaces 81 and 82, respectively, which fitcontiguous to a vertical surface 83 of arm 44.

An enlarged view of cards 67 and 74 is shown in FIG. 4 with card slot69, set screw 68 and arm 38 with indicia 71 on a card 84 fixed to arm38. A slot 85 extends all the way through arm 38. Lead screw 41 has beenomitted for clarity. A top plan view of the structure of FIG. 4 is shownin FIG. 5.

The manner in which set screw 68 fits through slot 69 and is threaded tocard 74 and clamps card 67 in a fixed position relative thereto isillustrated in FIG. 6.

FIGS. 7 and 8 illustrate how index marker 46 slides between arms 38 and44 if lead screw 41 is turned. As stated previously, index marker 46 isfixed to traveling nut 42. Projection 43 includes a shaft 86 fixed tonut 42 and a ball bearing 87 pressed onto shaft 86.

As shown in FIG. 9, if desired, index marker 46 may be fixed both toshaft 86 and to nut 42.

What is claimed is:

1. In a control system, a set point adjustment comprising: a support; afirst member; a first arrangement movably mounting said first member onsaid support in a manner such that at least one portion thereof ismovable between first and second positions over a path of travel; firstmeans mounted on said support and connected to said first member, saidfirst means being actuable to move said first member toward said firstposition along said path of travel thereof; a second member; a secondarrangement movably mounting said second member on said support in amanner such that at least one portion thereof is movable between firstand second positions over a path of travel closer to and farther awayfrom said first member, respectively, said second member being connectedto said first means in a manner to deactuate said first means when saidsecond member moves toward said first member, said first member beingfarther from said second member in said first member first position thanin said first member second position; a tension spring having one endconnected to the said portion of one of said members; second meansmounting the other end of said spring on the said portion of the otherof said members, said second means including a flexible strand havingone end fixed to the other end of said spring; a pulley; a thirdarrangement rotatably supporting said pulley on said other member, saidstrand being threaded around said pulley; and third means connectedbetween said other member and the other end of said strand and ajustablelengthwise therebetween to adjust the amount of tensile stress on saidspring.

2. The invention as defined in claim 1, wherein said third meansincludes a lead screw, means to hold said lead screw in a rotatable butotherwise fixed position relative to said other member, a nut threadedonto said screw fixed to said strand, an index marker threaded onto saidscrew, said nut and said marker being constructed and positioned to moveaxially on said screw when said screw is rotated, and a scale fixed tosaid other member in a position adjacent said marker to indicate the setpoint by the position of said marker relative thereto.

3. In a control system, the combination comprising: a support; a firstmember movably mounted on said support; a second member movably mountedon said support; a third member movably mounted on said support, saidfirst member being mounted on said support in a position in engagementwith said third member to be moved when said third member is moved;first means mounted on said support connected to said third member, saidfirst means being responsive to hydraulic pressure to move said thirdmember; a hydraulic pump mounted on said support; an inlet conduitconnected from said pump to said first means to supply fluid underpressure thereto; a hydraulic amplifier mounted on said support havingan inlet and an outlet, said amplifier having a valve to decrease theopening of said inlet as the pressure between said inlet and said outletincreases, and vice versa; a conduit connected from said inlet conduitto said amplifier inlet providing free and open communication ofhydraulic fluid therebetween; a bleed conduit connected from saidamplifier outlet having a bleed orifice therethrough; a balance beamhaving a flapper valve fixed thereto to vary the opening of saidorifice; second means to pivot said beam from said support near thecenter of said beam; a projection adjustably mounted on said firstmember; a tension spring connected from said second member to one end ofsaid beam in a position to bias said second member into engagement withsaid projection and accordingly to bias said first member intoengagement with said third member, said spring also tending to pivotsaid one beam end toward said second member; electromagnet means mountedon said support and the other end of said beam to provide a variableforce on said beam tending to place a tensile stress on said movement ofsaid one beam end toward said second member causing said flapper valveto open wider, and vice versa, adjustment of the position of saidprojection on said first member causing movement of said second memberrelative to said first and third members when said first and thirdmembers are held stationary; an index marker mounted on said firstmember; first and second cards fixed to said first member, said secondcard having indicia thereon to indicate bandwidth; a third card movablymounted relativeto said first and second cards, said third card havingindicia thereon extending from said index marker to said second cardindicia, one of said first and third cards having indicia thereonadjacent the other to indicate the stroke setting of said third card;and third means adjustably mounted relative to said first member to holdsaid third card releasably in a fixed position.

4. The invention as defined in claim 3, including a lead screw mountedin a rotatable angular but otherwise fixed position relative to saidfirst member, a nut threaded onto said lead screw, said nut beingpositioned in a manner such that it will not rotate relative to saidfirst member, said index marker being fixed to said nut, said projectionalso being fixed to said nut.

5. The invention as defined in claim 4, wherein said first and secondmembers are movable up and down generally in parallel planes, said indexmarker being slidable between said first and second members contiguousto each,

said third card having a slot therethrough, said third means including aset screw extending through said slot and being threaded into saidsecond card.

6. The invention as defined in claim 1, wherein said first meansincludes a cylinder fixed relative to said support, a piston rodslidable longitudinally in said cylinder, a piston fixed to said rod ina position sealing against said cylinder, a linkage connected betweensaid piston rod and said first member, a hydraulic pump, an inletconduit connected from said pump to said cylinder, a hydraulicarnplifier mounted on said support having an inlet and an outlet, saidamplifier having a valve to decrease the opening of said inlet as thepressure between said inlet and said outlet increases, and vice versa, aconduit connected from said inlet conduit to said amplifier inletproviding free and open communication of hydraulic fluid therebetween, ableed conduit connected from said amplifier outlet having a bleedorifice therethrough, a balance beam having a flapper valve fixedthereto to vary the opening of said orifice, second means to pivot saidbeam from said support near the center of said beam, said second memberincluding a longitudinal extension integral with said balance beam atone end thereof.

7. The invention as defined in claim 6, wherein said third meansincludes a lead screw, means to hold said lead screw in a rotatable butotherwise fixed position relative to said other member, a nut threadedonto said screw fixed to said strand, an index marker threaded onto saidscrew, said nut and said marker being constructed and positioned to moveaxially on said screw when said screw is rotated, and a scale fixed tosaid other member in a position adjacent said marker to indicate the setpoint by the position of said marker relative thereto.

References Cited UNITED STATES PATENTS 2,190,506 2/ 1940 Wurr 73-432 UX2,509,861 5/1950 Cooper 73-432 3,087,471 4/1963 Ray 91-28 3,101,0318/1963 Crossley, Jr. 91-364 3,193,030 7/1965 Meier 177-168 X LOUIS I.CAPOZI, Primary Examiner US. Cl. X.R. 73-432; 91-47

